Generally, antennas are devices which convert electric signals into electromagnetic waves and radiate the electromagnetic waves through air and vice versa. Patterns of effective areas onto or from which antennas can radiate or sense electromagnetic waves are generally referred to as radiation patterns.
In recent years, antennas having a very wide frequency band comprising a plurality of service bands or multi-band antennas operated in double or multiple frequency bands have been developed.
A plurality of antennas in a Multi-Band antenna are disposed on one side of a ground plate, causing interference to occur between the antennas. Thus, radiation patterns may be distorted or antenna elements may be combined with one another.
In a Multi-Band antenna system employing a monopole antenna, a radiation strip is folded a plurality of times so that the monopole antenna may be operated in multiple frequency bands.
As the number of folds of the radiation strip increases, the system may become complicated and the size of the antenna may increases. Accordingly, there is a need to efficiently arrange antennas in a Multi-Band antenna system, so that the antennas may be operated in multiple frequency bands, interference between antennas may be reduced, and the antennas may be fabricated to be small in size.